Heat treating systems for materials typically involve energy-intensive processes. In addition to high energy consumption during a heat treatment operation, considerable energy is typically wasted either while maintaining a heat treatment system in operational standby mode (e.g., while awaiting the arrival of parts to be heat treated), or while heating a heat treatment system to take it from a shut-down mode to an operational mode. In addition, many heat treatment systems utilize heat treating media that require a long time to heat to operational temperature. What are needed therefore are improved systems for heat treating that are more energy efficient and that may be started up more rapidly.